This proposal is an application for a Research Scientist Development Award (RSDA). The principal objective to be achieved during the tenure of the requested award is the pursuit of theoretical and empirical research on normal and disordered visual word recognition. Word recognition is a central component of reading and has also provided a domain in which to explore general issues concerning processing and the representation of knowledge. Impairments in this capacity are observed both developmentally and as a consequence of brain injury. The applican has been engaged in a program of research whose goal is the development of an integrated theory of normal and impaired lexical processing. A central aspect of this work is the implementation of detailed "connectionist" models of the lexicon. These models suggest general principles governing the acquisition of word processing skills and the nature of skilled performance. Developmental anomalies are simulated by changing the initial configuration of the network model; impairments following brain injury are simulated by "lesioning" the model of normal performance. The simulations are assessed with respect to behavioral data concerning performance on tasks such as reading words aloud and making word-nonword discriminations. On-going research uses both modeling and behavioral approaches to address current issues in word recognition; the division of labor among components of the lexical processing system; nonword pronunciation. The applicant's plan is to significantly enlarge the scope of the project during the period of the RSDA, in three respects: (a) developing the semantic component of the model; (b) simulating patterns of semantic impairment associated with different types of neuropathology (Alzheimer's disease, herpes encephalitis, stroke), and (c) exploring the application of the same computational principles to the processing of words in context. The RSD would provide release time from other commitments that would make it possible to pursue these new directions. The RSDA would also allow the applicant to acquire additional skills in computational modeling and in neurobiology needed in order to develop the research in these directions